Human-computer interaction has evolved considerably over the years. From good old command line based interfaces to present day multimodal interactive systems, developers are redefining the way people engage with computing devices. Intuitive interfaces are gaining importance. For example, touch based input is being increasingly preferred on handheld devices, such as, mobile phones, smart phones, PDAs (Personal Digital Assistant), touchpad, etc.
Speech is another modality that has been used either alone or in conjunction with other input modalities, such as, traditional keyboard, mouse input, gestures, gaze, etc. to interact with a computing device. Speech input may be used to convert spoken words into text, to provide commands or to control a computer application. For example, speech recognition has been used for voice dialing, performing a search, providing an interactive voice response, playing video games and controlling a robotic device.